Human thyroglobulin
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ABSTRACT:
SUBMITTER: Francesca Coscia
PROVIDER: EMPIAR-10666 | biostudies-other |
REPOSITORIES: biostudies-other
Publications
The structure of human thyroglobulin.
Coscia Francesca F Taler-Verčič Ajda A Chang Veronica T VT Sinn Ludwig L O'Reilly Francis J FJ Izoré Thierry T Renko Miha M Berger Imre I Rappsilber Juri J Turk Dušan D Löwe Jan J
Nature 20200205 7796
Thyroglobulin (TG) is the protein precursor of thyroid hormones, which are essential for growth, development and the control of metabolism in vertebrates<sup>1,2</sup>. Hormone synthesis from TG occurs in the thyroid gland via the iodination and coupling of pairs of tyrosines, and is completed by TG proteolysis<sup>3</sup>. Tyrosine proximity within TG is thought to enable the coupling reaction but hormonogenic tyrosines have not been clearly identified, and the lack of a three-dimensional struc ...[more]
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Project description:Thyroglobulin (TG) is the protein precursor of thyroid hormones, which are essential for growth, development and the control of metabolism in vertebrates1,2. Hormone synthesis from TG occurs in the thyroid gland via the iodination and coupling of pairs of tyrosines, and is completed by TG proteolysis3. Tyrosine proximity within TG is thought to enable the coupling reaction but hormonogenic tyrosines have not been clearly identified, and the lack of a three-dimensional structure of TG has prevented mechanistic understanding4. Here we present the structure of full-length human thyroglobulin at a resolution of approximately 3.5 Å, determined by cryo-electron microscopy. We identified all of the hormonogenic tyrosine pairs in the structure, and verified them using site-directed mutagenesis and in vitro hormone-production assays using human TG expressed in HEK293T cells. Our analysis revealed that the proximity, flexibility and solvent exposure of the tyrosines are the key characteristics of hormonogenic sites. We transferred the reaction sites from TG to an engineered tyrosine donor-acceptor pair in the unrelated bacterial maltose-binding protein (MBP), which yielded hormone production with an efficiency comparable to that of TG. Our study provides a framework to further understand the production and regulation of thyroid hormones.
| S-EPMC7170718 | biostudies-literature
Project description:Thyroglobulin is a large protein present in all vertebrates. It is synthesized in the thyrocytes and exported to lumen of the thyroid follicle, where its tyrosine residues are iodinated . The iodinated thyroglobulin is reintegrated into the cell and processed (cleaved to free its two extremities) for thyroid hormone synthesis. Thyroglobulin sequence analysis has identified four regions of the molecule: Tg1, Tg2, Tg3 and ChEL. Structural abnormalities and mutations result in different pathological consequences, depending on the thyroglobulin region affected. We carried out a bioinformatic analysis of thyroglobulin, determining the origin and the function of each region. Our results suggest that the Tg1 region acts as a binding protein on the apical membrane, the Tg2 region is involved in protein adhesion and the Tg3 region is involved in determining the three-dimensional structure of the protein. The ChEL domain is involved in thyroglobulin transport, dimerization and adhesion. The presence of repetitive domains in the Tg1, Tg2 and Tg3 regions suggests that these domains may have arisen through duplication.
| S-EPMC3464141 | biostudies-literature
Project description:The thyroglobulin (TG) protein is essential to thyroid hormone synthesis, plays a vital role in the regulation of metabolism, development and growth and serves as intraglandular iodine storage. Its architecture is conserved among vertebrates. Synthesis of triiodothyronine (T3) and thyroxine (T4) hormones depends on the conformation, iodination and post-translational modification of TG. Although structural information is available on recombinant and deglycosylated endogenous human thyroglobulin (hTG) from patients with goiters, the structure of native, fully glycosylated hTG remained unknown. Here, we present the cryo-electron microscopy structure of native and fully glycosylated hTG from healthy thyroid glands to 3.2 Å resolution. The structure provides detailed information on hormonogenic and glycosylation sites. We employ liquid chromatography-mass spectrometry (LC-MS) to validate these findings as well as other post-translational modifications and proteolytic cleavage sites. Our results offer insights into thyroid hormonogenesis of native hTG and provide a fundamental understanding of clinically relevant mutations.
| S-EPMC8748809 | biostudies-literature
Project description:An HLA-DR variant containing Arginine at position 74 of the DRbeta1 chain confers a strong genetic susceptibility to autoimmune thyroid diseases (AITD), Graves' disease (GD) and Hashimoto's thyroiditis (HT), while Glutamine at position DRbeta1-74 is protective. We hypothesized that the DRbeta1-Arg74 variant is able to present pathogenic thyroglobulin (Tg) peptides to T-cells more efficiently, thereby triggering thyroid autoimmunity. Indeed, we have previously identified 4 human Tg (hTg) peptides that bind specifically to DRbeta1-Arg74 with much weaker binding to the protective variant DRbeta1-Gln74. The aim of our study was to examine in vivo whether an hTg peptide that binds strongly and specifically to DRbeta1-Arg74 is capable of stimulating T-cells during the induction of thyroiditis in a "humanized" mouse expressing human DR3, and in patients positive for Tg antibodies. Sequencing of exon 2 of the DR transgene in the DR3 mice, null for endogenous MHC II molecules, confirmed that they expressed the disease-associated DRbeta1-Arg74 variant, thus making them an ideal in vivo model to test the presentation of hTg peptides by DRbeta1-Arg74 HLA-DR. Induction of EAT in the DR3 mice lead to T-cell stimulation and proliferation to Tg.2098, a strong and specific DRbeta1-Arg74 binder, while a non-binding control peptide, Tg.2766 did not induce this response. Moreover, Tg.2098 stimulated T-cells from 4 individuals who were positive for thyroglobulin antibodies, demonstrating that Tg.2098 is an immunogenic peptide capable of being presented in vivo and activating T-cells in EAT and AITD. Energetic analysis of the complex formed by Tg.2098 and DRbeta-Arg74 has shown that the origin of the affinity was determined by residues 1, 7 and 9 in the peptide, while the selectivity of the peptide for the MHC was determined by the Asp in position 4. The disease-protective substitution R74Q, leads to reduction in affinity due to changes in local interaction with D4 as well as non-local interaction with other residues. The electrostatic potential on the surface of the DRbeta-Arg74-Tg.2098 complex has a unique signature which may be recognized by T-cell receptors leading to autoimmune thyroiditis. Taken together these findings suggest that Tg.2098, a strong and specific binder to the disease-associated HLA-DRbeta-Arg74, is a major human T-cell epitope and participant in the pathoetiology of AITD.
| S-EPMC2878895 | biostudies-literature
Project description:Thyroid hormones T3 and T4 play a crucial role in the regulation of vertebrate metabolism. The thyroglobulin (Tg) protein is key to thyroid hormone synthesis, and its structure is conserved among vertebrates. TgG is delivered through the secretory pathway to the lumen of the thyroid gland, where it is iodinated at specific tyrosine sites to form mono- or di-iodotyrosine, which combine to produce T3 and T4, respectively. The formation of these hormones depends on the precise 3D structure of thyroglobulin, which has remained unknown despite decades of research on this protein. Here, we present the cryo-electron microscopy structure of human thyroglobulin, to a global resolution of 3.2 Å. Our results offer structural insight into thyroid hormonogenesis and provide a framework to understand hundreds of clinically relevant mutations. The structure of hTg contributes to a better understanding and potentially improved treatment of thyroid hypothyroidism, thyroid cancer and other Tg disorders.
2022-02-24 | PXD018452 | Pride
Project description:Interactions between two human iodothyronine-binding autoantisera and three preparations of human thyroglobulin (Tg) were not proportional to the latter's thyroxyl residue content. Probably only one of the several thyroxyl-containing sites in Tg reacted with the immunoglobulins from both antisera. In the case of one of the antisera, which was thyroxine (T4)-specific, the thyroxyl residue was the immunodominant feature of the antigenic site. The other antiserum, which had a specificity for 3,5,3'-tri-iodothyronine (T3), recognized different determinants around the same thyroxyl residue, but this residue was not itself an important element of the binding site. Thus, despite the specificity for T3 free in solution, the presence of T4 in the complete antigenic site was tolerated, since other structures supplied the bulk of the binding energy. 'Specificity' of this antiserum for T3 in solution is therefore coincidental and need not be ascribed to the presence of T3 in the original immunogen. Some results obtained in these studies may be interpreted as supporting the possibility that a modified Tg was the immunogen for the generation of these naturally occurring human antisera.
| S-EPMC1153886 | biostudies-other
Project description:Thyroglobulin protein is the precursor of thyroid hormones, which are essential for growth, development and control of metabolism in vertebrates. Hormone synthesis from thyroglobulin (TG) occurs in the thyroid gland via the iodination and subsequent coupling of pairs of tyrosine amino acids, whose positions in TG have not been clearly identified. Tyrosine proximity within TG is thought to enable the coupling reactions but the lack of a three-dimensional structure of TG has prevented mechanistic understanding. Here we determined the structure of full-length human thyroglobulin at ~3.4 Å resolution by cryo-electron microscopy (cryo-EM). To enable perturbation experiments we expressed human TG in human HEK cells and showed it to be active in hormone production. We identified all hormogenic tyrosine pairs in the structure and verified them via site-directed mutagenesis and in vitro hormone production assays. Analysis revealed that proximity, flexibility and solvent exposure of the tyrosines are key characteristics of the hormogenic sites. To support the validity of our insights, we engineered the small bacterial protein MBP (maltose binding protein) to produce thyroid hormones with similar efficiency as TG. Finally, our study provides an essential framework to further understand the production and regulation of thyroid hormones, including in thyroid diseases.
2020-02-06 | PXD014821 | Pride
Project description:ContextMeasurements of thyroglobulin (Tg) and Tg antibodies are crucial in the follow-up of treated differentiated thyroid cancer (DTC) patients. Interassay differences may significantly impact follow-up.ObjectiveThe aim of this multicenter study was to explore the impact of Tg and Tg antibody assay performance on the differential classification of DTC patients, as described in national and international guidelines.DesignFour commonly used Tg and Tg antibody assays were technically compared to reflect possible effects on patients with DTC follow-up. Storage stability at different storage temperatures was also investigated for LIAISON® and Kryptor assays, as this is an underexposed topic in current literature.ResultsB.R.A.H.M.S. assays yield approximately 50% lower Tg values over the whole range compared to the DiaSorin and Roche assays investigated. These differences between assays may result in potential misclassification in up to 7% of patients if fixed cutoffs (eg, 1 ng/mL) are applied. Poor correlation was also observed between the Tg antibody assays when the method-specific upper limits of normal are used as cutoffs. Storage of Tg and Tg antibodies was possible for 3 to 4 weeks at -20°C and -80°C. Calibration of the assays, however, was found to be crucial for stable results over time.ConclusionsTechnical aspects of Tg and Tg antibody assays, including interassay differences, calibration and standardization, and cutoff values, may have a significant clinical impact on the follow-up of DTC patients.
| S-EPMC8739647 | biostudies-literature
Project description:Iodine is an essential element required for the function of all organ systems. Although the importance of iodine in thyroid hormone synthesis and reproduction is well known, its direct effects on the immune system are elusive. Human leukocytes expressed mRNA of iodide transporters (NIS and PENDRIN) and thyroid-related proteins [thyroglobulin (TG) and thyroid peroxidase (TPO)]. The mRNA levels of PENDRIN and TPO were increased whereas TG transcripts were decreased post leukocyte activation. Flow cytometric analysis revealed that both PENDRIN and NIS were expressed on the surface of leukocyte subsets with the highest expression occurring on monocytes and granulocytes. Treatment of leukocytes with sodium iodide (NaI) resulted in significant changes in immunity-related transcriptome with an emphasis on increased chemokine expression as probed with targeted RNASeq. Similarly, treatment of leukocytes with NaI or Lugol's iodine induced increased protein production of both pro- and anti-inflammatory cytokines. These alterations were not attributed to iodide-induced de novo thyroid hormone synthesis. However, upon incubation with thyroid-derived TG, primary human leukocytes but not Jurkat T cells released thyroxine and triiodothyronine indicating that immune cells could potentially influence thyroid hormone balance. Overall, our studies reveal the novel network between human immune cells and thyroid-related molecules and highlight the importance of iodine in regulating the function of human immune cells.
| S-EPMC5694785 | biostudies-literature
Project description:Thyroid hormones are essential for the metabolism of vertebrates and their synthesis, storage and release in the thyroid gland are orchestrated by their large protein precursor thyroglobulin (Tg). Alterations of Tg structure and localisation often correlate with major thyroid disorders. Namely, Tg is the main antigen in autoimmune thyroid diseases, and mutations in its gene are one of the causes of congenital hypothyroidism. Post-translational modifications (PTMs) are crucial for Tg surface properties and may be affected by the disease microenvironment; yet, their role in thyroid homeostasis and pathogenesis remains elusive. The advance of electron cryo-microscopy (cryo-EM) has recently enabled the structure of Tg to be revealed in the un-iodinated and iodinated states. Moreover, ad hoc proteomic analyses have lately identified new PTMs in Tg. Here, we provide an overview of the Tg cryo-EM models obtained so far, and we build a three-dimensional map of known PTMs in Tg. Based on their location, we suggest the potential implication of each PTM in hormonogenesis, interactions with cellular partners, colloid cross-linking and hormone release. In addition, several PTMs overlap with immunogenic regions and pathogenic gene mutations. Hence, our analysis reveals a possible cross-talk between PTMs and alteration of Tg function in these disorders. In perspective, multi-omics analyses from patients, interpreted with structural and functional data, may generate more robust models to correlate phenotypes with classes of Tg functional alterations. This integrative approach will likely provide more targeted strategies to restore specific Tg functions in different thyroid pathologies.
| S-EPMC9254275 | biostudies-literature